【Flutter】Wi-Fiを取得し、通信状況を確認する方法ご紹介。〜 connectivity使用 〜

dev_dependencies:
  connectivity: ^2.0.2
  flutter_test:
    sdk: flutter

import 'dart:async';
import 'dart:io';

import 'package:connectivity/connectivity.dart';
import 'package:flutter/foundation.dart';
import 'package:flutter/material.dart';
import 'package:flutter/services.dart';

// Sets a platform override for desktop to avoid exceptions. See
// https://flutter.dev/desktop#target-platform-override for more info.
void _enablePlatformOverrideForDesktop() {
  if (!kIsWeb && (Platform.isWindows || Platform.isLinux)) {
    debugDefaultTargetPlatformOverride = TargetPlatform.fuchsia;
  }
}

void main() {
  _enablePlatformOverrideForDesktop();
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  final String title;

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  String _connectionStatus = 'Unknown';
  final Connectivity _connectivity = Connectivity();
  StreamSubscription<ConnectivityResult> _connectivitySubscription;

  @override
  void initState() {
    super.initState();
    initConnectivity();
    _connectivitySubscription =
        _connectivity.onConnectivityChanged.listen(_updateConnectionStatus);
  }

  @override
  void dispose() {
    _connectivitySubscription.cancel();
    super.dispose();
  }

  // Platform messages are asynchronous, so we initialize in an async method.
  Future<void> initConnectivity() async {
    ConnectivityResult result;
    // Platform messages may fail, so we use a try/catch PlatformException.
    try {
      result = await _connectivity.checkConnectivity();
    } on PlatformException catch (e) {
      print(e.toString());
    }

    // If the widget was removed from the tree while the asynchronous platform
    // message was in flight, we want to discard the reply rather than calling
    // setState to update our non-existent appearance.
    if (!mounted) {
      return Future.value(null);
    }

    return _updateConnectionStatus(result);
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('Connectivity example app'),
      ),
      body: Center(child: Text('Connection Status: $_connectionStatus')),
    );
  }

  Future<void> _updateConnectionStatus(ConnectivityResult result) async {
    switch (result) {
      case ConnectivityResult.wifi:
      case ConnectivityResult.mobile:
      case ConnectivityResult.none:
        setState(() => _connectionStatus = result.toString());
        break;
      default:
        setState(() => _connectionStatus = 'Failed to get connectivity.');
        break;
    }
  }
}